Cawood.
I don't go by hearsay, I was reading some tests done by certain people and Mobil 1 did not do very well, particularly for retaining viscosity ie it got thin and runny, but by No means as bad as CASTROL R.
Moby did not do so well in wear tests either, it must be remembered that the test were some of THE top oils, so any that get there are still excellent.
Real shockers for bad performance were CASTROL R, CASTROL SLX, ROYAL PURPLE.
From my own experience with MOBIL 1, I would not use it again, from the noise of the very hard worked engine it was obvious it was getting thin and castrol RS was even worse.
Don't get me wrong it is a excellent oil, but if you can have better you would wouldn't you ?
tabetha